Abstract: Objective:To explore the effects of eriC^F1 and eriC^F2 genes under the condition of different fluoride concentrations on the fluoride resistance of Streptococcus mutans(S.mutans) fluoride-resistant strain UA159-FR, and to elucidate the relationship between the differential expressions of eriC^F genes and the fluoride resistance of S.mutans fluoride-resistant strain. Methods:The recombinant E.coli competent cells BL21 were divided into eriC^F1 group (eriC^F1 + Peasy-Blunt E2), eriC^F2 group (eriC^F2 + Peasy-Blunt E2) and KZ group (Peasy-Blunt E2). After gene cloning and IPTG induction, the expression levels of EriC^F1 and EriC^F2 proteins in three groups were detected, and the concentrations of bacterial solution and the growth rates of bacterium of strains in three groups were determined under different concentrations of fluoride conditions (1.5,2.0,2.5,and 3.0 g·L^-1 sodium fluoride);the growth curves were drawn. Results:At logarithmic phase(8 h) and stable phase(16 h), the final concentrations of bacterial solution and the growth rates of the strains in three groups under different concentrations of fluorine environments (1.5,2.0,2.5 and 3.0 g·L^-1 sodium fluoride) were compared in the same group,and the final concentrations and the growth rates of bacterial solution of the strains in three groups were decreased with the increasing of sodium fluoride concentration; the final concentrations and the growth rates of bacterial solution results were eriC^F2 group > eriC^F1 group > KZ group (P<0.05 or P<0.01).compared between three groups under the same concentration of sodium fluoride, the concentration of bacterial solution in eriC^F2 group was increased significantly compared with eriC^F1 group(P<0.01). Conclusion:Both eriC^F1 and eriC^F2 genes can enhance the fluoride resistance of E.coli, and the fluoride resistance of E.coli expressing eriC^F2 gene is stronger than that of E.coli expressing eriC^F1 gene.

Key words: eriC^F1, eriC^F2, Streptococcus mutans, fluoride-resistant strains of Streptococcus mutans, fluorine resistance